A term that surfaces frequently at this time of the year is "Indian Summer". No one knows exactly where it originated, although it traces back to the 1770s. In Europe, the same season is variously known as All-Hallow Summer, Old Wife's Summer, Second Summer, St. Martin's or St. Luke's summer, and even God's Gift to Poland. Indian Summer can arrive any time from late September to mid-November. That's because the season is triggered by a specific event: the first frost of the fall. Indian summer typically takes the form of a string of warm, dry days and cool nights following an autumnal freeze. For many Kansans, it's considered the best season of the year and perfect for outdoor fun.
Mary Knapp, Weather Data Library